Bullying is a social phenomenon. About 30% of school children are involved in bullying as victims, bullies, or bully/victims. The victims of bullying suffer multiple negative consequences, including poor social and academic adjustment, depression, and anxiety. This paper extends Farrington and Ttofi's (2009) meta-analysis of controlled trials of 44 bullying interventions, which suggests that bullying programs are effective in decreasing bullying and victimization. We review controlled trials of bullying interventions published from June, 2009 through April, 2013, focusing on substantive results across 32 studies that examined 24 bullying interventions.

Although the overall findings are mixed, the data suggest that interventions implemented outside of the United States with homogeneous samples are more successful than programs implemented in the United States, where samples tend to be more heterogeneous. Few studies have measured bullying with sufficient precision to have construct validity. Finding strong measures to assess the complex construct of bullying remains a major challenge for the field.